1. Field of the Invention
The present application relates generally to wireless networking, and more particularly to systems and methods for supporting the use of mobile devices having multiple heterogeneous network access interfaces, whereby such mobile devices may connect to different wireless networks and/or make use of various network access technologies, for multiple purposes such as preventing the loss of data transmission packets and also to enhance the useable bandwidth of such mobile devices.
2. General Background Discussion
Internet Protocol
IP is a connectionless protocol. The connection between end points during a communication is not continuous. When a user sends or receives data or messages, the data or messages are divided into components known as packets. Every packet is treated as an independent unit of data.
In order to standardize the transmission between points over the Internet or the like networks, an OSI (Open Systems Interconnection) model was established. The OSI model separates the communications processes between two points in a network into seven stacked layers, with each layer adding its own set of functions. Each device handles a message so that there is a downward flow through each layer at a sending end point and an upward flow through the layers at a receiving end point. The programming and/or hardware that provides the seven layers of function is typically a combination of device operating systems, application software, TCP/IP and/or other transport and network protocols, and other software and hardware.
Typically, the top four layers are used when a message passes from or to a user and the bottom three layers are used when a message passes through a device (e.g., an IP host device). An IP host is any device on the network that is capable of transmitting and receiving IP packets, such as a server, a router or a workstation. Messages destined for some other host are not passed up to the upper layers but are forwarded to the other host. In the OSI and other similar models, IP is in Layer-3, the network layer. The layers of the OSI model are listed below.
Layer 7 (i.e., the application layer) is a layer at which, e.g., communication partners are identified, quality of service is identified, user authentication and privacy are considered, constraints on data syntax are identified, etc.
Layer 6 (i.e., the presentation layer) is a layer that, e.g., converts incoming and outgoing data from one presentation format to another, etc.
Layer 5 (i.e., the session layer) is a layer that, e.g., sets up, coordinates, and terminates conversations, exchanges and dialogs between the applications, etc.
Layer-4 (i.e., the transport layer) is a layer that, e.g., manages end-to-end control and error-checking, etc.
Layer-3 (i.e., the network layer) is a layer that, e.g., handles routing and forwarding, etc.
Layer-2 (i.e., the data-link layer) is a layer that, e.g., provides synchronization for the physical level, does bit-stuffing and furnishes transmission protocol knowledge and management, etc. The Institute of Electrical and Electronics Engineers (IEEE) sub-divides the data-link layer into two further sub-layers, the MAC (Media Access Control) layer that controls the data transfer to and from the physical layer and the LLC (Logical Link Control) layer that interfaces with the network layer and interprets commands and performs error recovery.
Layer 1 (i.e., the physical layer) is a layer that, e.g., conveys the bit stream through the network at the physical level. The IEEE sub-divides the physical layer into the PLCP (Physical Layer Convergence Procedure) sub-layer and the PMD (Physical Medium Dependent) sub-layer.
Typically, layers higher than layer-2 (such as layers including the network layer or layer-3 in the OSI model and the like) are referred to as the higher-layers.
Wireless Networks
Wireless networks can incorporate a variety of types of mobile devices, such as cellular and wireless telephones, PCs (personal computers), laptop computers, wearable computers, cordless phones, pagers, headsets, printers, PDAs, etc. For example, mobile devices may include digital systems to secure fast wireless transmissions of voice and/or data.
Wireless LANs (WLANs) in which a mobile user can connect to a local area network (LAN) through a wireless connection may be employed for wireless communications. Wireless communications can include communications that propagate via electromagnetic waves, such as light, infrared, radio, microwave. There are a variety of different WLAN standards that currently exist, such as Bluetooth, IEEE 802.11, and HomeRF.
For example, Bluetooth products may be used to provide links between mobile computers, mobile phones, portable handheld devices, personal digital assistants (PDAs), and other mobile devices and connectivity to the Internet. Bluetooth is a computing and telecommunications industry specification that details how mobile devices can easily interconnect with each other and with non-mobile devices using a short-range wireless connection. Bluetooth creates a digital wireless protocol to address end-user problems arising from the proliferation of various mobile devices that need to keep data synchronized and consistent from one device to another, thereby allowing equipment from different vendors to work seamlessly together. Bluetooth devices may be named according to a common naming concept. For example, a Bluetooth device may possess a Bluetooth Device Name (BDN) or a name associated with a unique Bluetooth Device Address (BDA). Bluetooth devices may also participate in an Internet Protocol (IP) network. If a Bluetooth device functions on an IP network, it may be provided with an IP address and an IP (network) name. Thus, a Bluetooth Device configured to participate on an IP network may contain, e.g., a BDN, a BDA, an IP address and an IP name. The term “IP name” refers to a name corresponding to an IP address of an interface.
Similarly, IEEE 802.11 specifies technologies for wireless LANs and devices. Using 802.11, wireless networking may be accomplished with each single base station supporting several devices. In some examples, devices may come pre-equipped with wireless hardware or a user may install a separate piece of hardware, such as a card, that may include an antenna. By way of example, devices used in 802.11 typically include three notable elements, whether or not the device is an access point (AP), a mobile station (STA), a bridge, a PCMCIA card or another device: a radio transceiver; an antenna; and a MAC (Media Access Control) layer that controls packet flow between points in a network.
Wireless networks also may involve methods and protocols found in Mobile IP (Internet Protocol) systems, in PCS systems, and in other mobile network systems. With respect to Mobile IP, this involves a standard communications protocol created by the Internet Engineering Task Force (IETF). With Mobile IP, mobile device users may move across networks while maintaining their IP Address assigned once. See Request for Comments (RFC) 3344. Mobile IP enhances Internet Protocol (IP) and adds means to forward Internet traffic to mobile devices when connecting outside their home network. Mobile IP assigns each mobile node a home address on its home network and a care-of-address (CoA) that identifies the current location of the device within a network and its subnets. When a device is moved to a different network, it receives a new care-of address. A mobility agent on the home network can associate each home address with its care-of address. The mobile node can send the home agent a binding update each time it changes its care-of address by using a protocol such as Internet Control Message Protocol (ICMP).
In basic IP routing, routing mechanisms typically rely on the assumptions that each network node always has a constant attachment point to the Internet and that each node's IP address identifies the network link it is attached to. In this document, the terminology “node” includes a connection point, which can include a redistribution point or an end point for data transmissions, and which can recognize, process and/or forward communications to other nodes. For example, Internet routers can look at an IP address prefix or the like identifying a device's network. Then, at a network level, routers can look at a set of bits identifying a particular subnet. Then, at a subnet level, routers can look at a set of bits identifying a particular device. With typical mobile IP communications, if a user disconnects a mobile device from the Internet and tries to reconnect it at a new subnet, then the device has to be reconfigured with a new IP address, a proper netmask and a default router. Otherwise, routing protocols would not be able to deliver the packets properly.
Handoffs of Mobile Devices
In the context of a mobile device with an IP-based wireless network interface, the mobile device needs to perform roaming or handoffs when it moves from one network to another network, or from one access point of a network to another. With existing handoff methodologies, handoff is typically accomplished by performing the following sequence of protocol layer specific handoffs:                First, handoff takes place at the physical layer. In this regard, the mobile device switches its radio channel to a wireless base station or wireless access point in the target network.        Second, handoff takes place at layer-2. In this regard, the mobile device switches its layer-2 (i.e., link-layer) connections to the target network. As explained above, the link layer or layer-2 refers to the protocol immediately below the IP-layer that carries user traffic. The mobile device performs layer-2 authentication with the target network if the target network requires such authentication.        Third, handoff takes place at the IP-layer. In this regard, the mobile device obtains a local IP address from the target network, performs IP-layer authentication if required by the target network, and then performs IP-layer location update so that IP packets destined to the mobile device can be routed by the IP network to the mobile device via the target network. In some instances, one way to support IP layer location update is to use Mobile IP defined by the Internet Engineering Task Force (IETF).        Fourth, handoff takes place at the application-layer. The mobile device performs necessary steps at the application layer to ensure that its application traffic will flow correctly to the applications on the mobile device via the target network. For example, when the mobile device uses the Session Initiation Protocol (SIP) defined by the IETF to manage its application-layer signaling, an application layer handoff can be achieved by the mobile device updating its current location with its home SIP server. The mobile device may also need to carry out application-layer authentication with the target network if required by the target network. This is the case, for example, when the mobile device is using the IP Multimedia Subsystem (IMS) in a visited 3GPP (3rd Generation Partnership Project) wireless network, where the IMS is a SIP-based system supporting application-layer signaling and management for multimedia applications over 3GPP networks.Multiple Network Access Interface Mobile Devices        
As the popularity and proliferation of wireless network access grows, more and more mobile devices are expected to have Multiple Interface Device (MID) capabilities. MIDs are mobile devices that contain two or more independent network interfaces, thus allowing the MID to have connectivity with two or more separate networks and/or make use of different network access technologies. The MID may have an IP address and a common IP (network) name associated with the IP address.
For example, an MID may have different wireless local-area (WLAN) interfaces such as 802.11x (i.e., IEEE 802.11a, 802.11b or 802.11g), BlueTooth, HomeRF, or Wi-Fi, different wide-area (WAN) radio interfaces such as GPRS (General Packet Radio Service), 3G, 3GPP, 3GPP2, GSM (Global System for Mobile Communications), EDGE (Enhanced Data for GSM Evolution), TDMA (Time Division Multiple Access), or CDMA (Code Division Multiple Access), both WLAN and WAN wireless network interfaces, or both wireless and wireline network interfaces.
Each network interface may contain addresses of varying types, such as an IP address, a Bluetooth Device Address, a Bluetooth Common Name, a Bluetooth IP address, a Bluetooth IP Common Name, an 802.11 IP Address, an 802.11 IP common Name, or an IEEE MAC address.
MIDs therefore provide flexibility in allowing a user to gain access to more than one type of wireless network with a single mobile device. However, additional benefits could be reaped if the MID mobile device could use the multiple network interfaces to optimize the user's communication experience. For example, when a mobile device is traveling (either in a vehicle or being carried by the user on foot) in an active session through regions of different network providers or different access point technologies, it is prone to losing data packets, which may impair real-time sensitive applications such as VoIP (Voice Over IP) or streaming media applications. In this situation, the multiple interfaces could be used beneficially for packet loss recovery. On the other hand, when a mobile device user is stationary, packet loss is not as much of a concern. Therefore in a stationary situation, the multiple interfaces could be used advantageously to increase or enhance bandwidth. The enhanced bandwidth may be useful, for example, in running high data rate applications or in sharing the load of a congested network.
FIG. 7 shows an example of a MID mobile device 1 including a plurality of interfaces. In the illustrated example, three interfaces are shown: Interface 1; Interface 2 and Interface 3. However, any number of interfaces can be employed. In illustrative embodiments, a MID device can include portable computers, personal desk-top computers, PDAs, portable voice-over-IP telephones and/or other devices. Typically, such mobile devices will include a transceiver (including an antenna for communication with the access point), a processor, memory (including program memory and Random Access Memory). As also shown, the memory can include a program or module, such as a QoI Comparison Module for carrying out functionality as described hereinafter. In various embodiments, processes to be carried out by the MID can be performed via software, hardware and/or firmware as may be appropriate based on circumstances.
As shown in FIG. 7, mobile MID 1 is capable of communication over a plurality of heterogeneous networks via separate interfaces 1-3. For example, the mobile device can communicate via an Access Point 22 (such as a wireless LAN (WLAN) access point) or via a Base Station 2 (such as a WAN base station). Although not specifically applicable to the concepts of the present invention, FIG. 7 also shows that the MID 1 may also be able to communicate with a wired network. The Access Point 22 can be within a wireless local area network (WLAN) connected to a wireline network 20. The wireline network 20 can include the Internet or a corporate data processing network. The access point 22 also can be a wireless router having a network interface 25 linked to the wireline network 21 and a wireless transceiver in communication with the mobile device 1 as well as with other mobile devices. The wireless transceiver 26 can include an antenna 27 for radio or microwave frequency communication with the mobile devices. The Access Point 22 preferably also has a processor 28, a program memory 29, and a random access memory 31.
In general, processes are known that address packet loss prevention or Quality of Interface (QoI) measurement. Several solutions have been suggested to take advantage of heterogeneous radio technologies. These can be grouped into two categories. One considers QoI comparisons at the Physical Layer. These solutions primarily take into account Signal Strength, SNR, or sending probes to network(s) and obtaining a series of measurements of available bandwidth from different interfaces. The other category considers IP Packets received at the IP Layer. Such solutions mainly take into account a quantitative comparison of the number of IP packets received on each IP stream. However, such processes represent partial solutions only, and do not provide a solution to the issues discussed above with respect to the dynamic use of multiple network interfaces for different purposes depending upon the stationary/moving status of the mobile device. Additionally, the known solutions pertaining to both categories each have various drawbacks or weaknesses. Consequently, there remains a need in the art for solutions to the above issues and problems related to improved and enhanced functionality of wireless MIDs.